Method for automatic frequency adaptation of a filter in a closed loop

Patent metadata

Field	Value
Publication number	US-11513135-B2
Application number	US-201916682328-A
Country	US
Kind code	B2
Filing date	Nov 13, 2019
Priority date	Nov 13, 2018
Publication date	Nov 29, 2022
Grant date	Nov 29, 2022

Abstract

A method adapts a resonant frequency of a first filter of a closed control loop to a given frequency. The method includes feeding an output signal of a delta sigma modulator of the closed control loop into a frequency adaptation circuit and determining a first noise spectrum of the output signal in a first frequency band and a second noise spectrum of the output signal in a second frequency band. The first frequency band and the second frequency band are arranged symmetrically with respect to the given frequency. The method includes comparing the first noise spectrum with the second noise spectrum, generating an adaptation signal that causes a frequency adaptation of the resonant frequency if the first noise spectrum differs from the second noise spectrum, and outputting the adaptation signal from the frequency adaptation circuit to a control input of the first filter for adapting the resonant frequency.

First claim

What is claimed is:

1. A method for adapting a resonant frequency of a first filter of a closed control loop to a given frequency, comprising:
feeding an output signal of a delta sigma modulator of the closed control loop into a frequency adaptation circuit;
determining a first noise spectrum of the output signal of the delta sigma modulator in a first frequency band and a second noise spectrum of the output signal of the delta sigma modulator in a second frequency band in the frequency adaptation circuit, the first frequency band and the second frequency band are arranged symmetrically with respect to the given frequency;
comparing the first noise spectrum in the first frequency band with the second noise spectrum in the second frequency band;
generating an adaptation signal that causes a frequency adaptation of the resonant frequency if the first noise spectrum differs from the second noise spectrum; and
outputting the adaptation signal from the frequency adaptation circuit to a control input of the first filter for adapting the resonant frequency.

2. The method of claim 1 , wherein in the comparing step, the first frequency band and the second frequency band are each demodulated individually into a baseband.

3. The method of claim 2 , wherein in the comparing step, a noise power in the first frequency band is compared with a noise power in the second frequency band or a signal strength in the first frequency band is compared with a signal strength in the second frequency band.

4. The method of claim 1 , wherein the first frequency band with a predetermined width is determined with respect to a first frequency and the second frequency band with a predetermined width is determined with respect to a second frequency.

5. The method of claim 4 , wherein the first frequency and the second frequency are provided by a further closed control loop having a second filter or a mechanical resonator with the given frequency as a further resonant frequency.

6. The method of claim 5 , wherein the first filter represents a movement of a secondary mass and the second filter or the mechanical resonator represents a movement of a primary mass of a rotation rate sensor.

7. The method of claim 1 , wherein the first noise spectrum and the second noise spectrum in the frequency adaptation circuit are determined in a digital domain or in an analog domain.

8. A signal processing device, comprising:
a closed control loop with a first filter having a resonant frequency and a delta sigma modulator; and
a frequency adaptation circuit receiving an output signal of the delta sigma modulator, determining a first noise spectrum of the output signal of the delta sigma modulator in a first frequency band and a second noise spectrum of the output signal of the delta sigma modulator in a second frequency band, the first frequency band and the second frequency band being arranged symmetrically with respect to a given frequency, comparing the first noise spectrum in the first frequency band with the second noise spectrum in the second frequency band, generating an adaptation signal that causes a frequency adaptation of the resonant frequency if the first noise spectrum differs from the second noise spectrum, and outputting the adaptation signal to a control input of the first filter for adapting the resonant frequency to the given frequency in response to the comparison result.

9. The signal processing device of claim 8 , wherein the frequency adaptation circuit includes a first demodulator branch and a second demodulator branch that extract the first noise spectrum in the first frequency band and the second noise spectrum in the second frequency band.

10. The signal processing device of claim 9 , wherein the first demodulator branch includes a first multiplier multiplying the output signal of the delta sigma modulator with a first comparison frequency that is higher than the given frequency.

11. The signal processing device of claim 10 , wherein the second demodulator branch includes a second multiplier multiplying the output signal of the delta sigma modulator with a second comparison frequency that is lower than the given frequency, the first comparison frequency and the second comparison frequency are arranged symmetrically to the given frequency.

12. The signal processing device of claim 11 , wherein the frequency adaptation circuit includes an adder and each of the first demodulator branch and the second demodulator branch has a respective squarer, the outputs of the squarers are connected to the adder, which determines a difference between the signals applied to the outputs of the squarer and outputs a differential value.

13. The signal processing device of claim 11 , wherein the frequency adaptation circuit includes an adder and each of the first demodulator branch and the second demodulator branch has a respective absolute-value element determining an absolute value, the outputs of the absolute-value elements are connected to the adder, which determines a difference between the signals applied to the outputs of the absolute-value elements and outputs a differential value.

14. The signal processing device of claim 12 , further comprising a controller connected to the adder, the controller generating the adaptation signal from the differential value.

15. The signal processing device of claim 11 , further comprising an additional closed control loop having a second filter or a mechanical resonator with the given frequency as a further resonant frequency.

16. The signal processing device of claim 15 , wherein the additional closed control loop has a phase-locked control loop providing the first comparison frequency and the second comparison frequency.

17. The signal processing device of claim 8 , wherein the frequency adaptation circuit determines the first noise spectrum and the second noise spectrum in a digital domain or in an analog domain.

18. A circuit arrangement for reading a capacitive rotation rate sensor, comprising:
a signal processing device including a closed control loop with a first filter having a resonant frequency and a delta sigma modulator, and a frequency adaptation circuit receiving an output signal of the delta sigma modulator, the frequency adaptation circuit determining a first noise spectrum of the output signal of the delta sigma modulator in a first frequency band and a second noise spectrum of the output signal of the delta sigma modulator in a second frequency band, the first frequency band and the second frequency band being arranged symmetrically with respect to a given frequency, comparing the first noise spectrum in the first frequency band with the second noise spectrum in the second frequency band, generating an adaptation signal that causes a frequency adaptation of the resonant frequency if the first noise spectrum differs from the second noise spectrum, and outputting the adaptation signal to a control input of the first filter for adapting the resonant frequency to the given frequency in response to the comparison result; and
a control unit configured to calculate and output a rotation rate signal based on the output signal of the delta sigma modulator.

19. The circuit arrangement of claim 18 , wherein the given frequency is a frequency of a primary oscillation of the capacitive rotation rate sensor, the capacitive rotation rate sensor having a primary mass and a secondary mass connected to the primary mass, the primary mass being excited to the primary oscillation during operation and the secondary mass being deflected from a position

Assignees

• Univ Freiburg Albert Ludwigs

Inventors

• Marx Maximilian
• De Dorigo Daniel
• Manoli Yiannos
• Cuignet Xavier

Classifications

• H03L7/093

  using special filtering or amplification characteristics in the loop (H03L7/087 - H03L7/091 take precedence) · CPC title

• G01C19/5776 Primary

  Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title

• H03M3/396

  among different frequency bands · CPC title

• G01P3/4802 Primary

  by using electronic circuits in general · CPC title